Thermostatic control



A TTORNEYJ 3 Sheets-Sheet l s; E. SKINNER THERMOSTATIC CONTROL Filed Feb 28, 1925 June 5, I928.

June 5, 1928.

S. E. SKINNER THERMOS'IATIC CONTROL Filed Feb. 28, 1925 5 Sheets-Sheet June 5, 1928.

s. E. SKIN NER THEHMOSTATIC CONTROL Filed Feb. 28, 1925 s Sheets-Sheqt 5 BY flaw ATTORNEY Patented June 5, 1928.

UNITED STATES PATENT OFFICE.

SHERROD E. SKINNER, OF NEW BRITAIN, CONNECTICUT, AS SIGNOB TO LANDERS,

FRARY &; CLARK, OF NEW BRITAIN,

NECTICUT.

CONNECTICUT, A CORPORATION OF CON- THERMOSTATIC CONTROL.

Application filed February 28, 1925. Serial No. 12,222.

This invention relates to improvements in thermostatic controls and more particularly to thermostatic controls for electric ovens.

It is the principal object of the invention to provide a thermostatic control that is unlformly reliable in its operation and that has a high degree of durability. More specifically it is an object of the invention to provide a thermostatic control that avoids the use of relays and return springs.

With these general objects in view the invention consists in the combinations, features, details of construction and arrangements of parts which will first be described in connection with the accompanying drawings and then more particularly pointed out.

In the drawings:

Figure 1 is a view in side elevation, with parts in section and parts broken away, of a thermostatic control constructed in accordance with the invention;

Figure 2 is a view of the same in front elevation, with parts broken away and in section;

I iigure 3 is a face view of the adjusting dia Figure 4 is a sectional view thereof;

Figures 5, 6, 7 and 8 are explanatory views showing diagrammatically the parts shown in Fig. 2, in various positions;

Figure 9 is a top plan view of the thermostatic control associated with an oven, the oven being indicated more or less diagrammatically;

Figure 10 is a sectional View of the make and-break device in closed circuitposition;

Figure 11 is a view of the same in open circuit position; and,

Figure 12 is a wiring diagram.

Referring to the drawings, the exemplification of the invention here illustrated com prises a bracket 21 arranged for attachment to the outside of an oven 20, for example, the rear wall. This bracket su ports all ofthe parts except a portion of tile adjusting device. There is provided a temperature-responsive element which, in structures embodying the invention to the best advantage, is made up of two common metals having different coefiicients of expansion. As here shown as an example, the temperature-responsive element comprises a long brass tube 22, the outer end of which is secured, in any suitable manner, to the bracket 21 which acts as an anchoring element for the tube. Enclosed within this brass tube is a steel bar 23. At the free end of the brass tube, the latter is adjustably secured to the steel bar. As shown, this is accomplished by a coupling nut 24 having a skirt portion threaded onto the end of the brass tube. Inside the coupling nut is a lock nut 25. The end of the rod is slightly reduced in diameter (Fig. 1) and adjacent the shoulder formed thereby is secured a stop collar 26 which engages a shoulder 27 formed on the coupling nut 24. On the end of the rod 23' are threaded two check nuts 28, 29. This construction adjustably ties the ends of the tube and rod together. The free end of the steel rod passes through a suitable hole in the bracket 21 and. is connected, as later described, to a leverage system connecting it with the circuit make-and-break device.

The temperature-responsive element, as will be understood, extends into the oven 20. In the embodiment illustrated an electric resistance heating unit 19, indicated diagrammatically in Fig. 9, is located near the bottom of the oven chamber. The temperature-responsive element is located below the unit 19 and in close proximity thereto. Moreover, it is substantially coextensive with one dimension of the heating unit. The oven and unit shown (Fig. 9) are rectangus lar in shape and the temperature-responsive element, as appears in the drawing, is substantially coextensive with the longer dimension. This makes possible a relatively large expansion movement. With the arrangement described the temperature-responsive element receives the first rush of heat, uniform throughout its length, so that there is substantially no lag in its operation.

As the oven temperature rises, the brass tube '22 being anchored at its inner end expands outwardly, i. e., away from its anchorage. The steel bar 23 being tied to the free end of the brass tube tends to expand in the opposite direction but as the coefiicient of expansion of brass is relatively much higher than steel, the resultant movement of expansion is such that the steel bar moves with the brass tube, i. e., to the left as viewed in circuit in any suitable manner.

Fig. 1. Conversely, upon contraction, when the oven cools, the movement of the steel bar is to the right with the tube.

\Vith the construction described, the action is easily controlled. The element comprises two common metals in commercial form. The coefficient of expansion of each being known, the amount of expansion and contraction for a given temperature is readily determined. Further, the element is capable of use with relatively high temperatures; is practically indestructible and return springs are avoided as the parts, after expansion, are positively returned by movement of contraction.

There is provided a make-and-break device for the heating circuit and a connection between the make-andbreak device and the temperature-responsive element. \Vhile the make-and-break device may vary, structures embodying the invention to the best advantage include a switch carried by a tilting cradle and operated by the tilt thereof. This may conveniently take the form of a mercury tube switch. As here shown as an example, the make-and-break device is in the form of a closed glass tube 30 containin a quantity of mercury 31. The tube has (F ig. 10), on its lower side, two small chambers 32, 33 communicating with the main portion of the tube. Extending into these chambers are terminals 34, 35, connected by couplings 36, 37, with circuit wires 38, 39. The switch may be connected up with the oven heating As indicated, as an example, in the wiring diagram of Fig. 12 the circuit wire 39 is connected with the one line wire 40, the wire 38 being connected with one terminal of the electric heating device 19. The other terminal of the heating device is connected, through a usual on-and-otf switch 42, with the second line wire 43. When the tube 30 is in a horizontal or nearly horizontal position, the mercury fills both chambers 32, 33 (Fig. 10) and the intervening space and thus acts as a conducting connection between the terminals 33, 34, so that the circuit is closed. When, however, the tube is tipped to a position such as shown in Fig. 11, there is a mercury flow into the low end of the tube, which breaks the mercury connection, whereby the circuit is opened. As shown in Fig. 11, however, the tilt of the tube is not so great as to cause the mercury to flow out of chamber 32. Themercury remaining in the chamber 32 continues to envelope terminal 34 so that the break is mercury to mercur and not mercury to metal. The means or limiting the tilt of the tube is later described. As here shown as an example, the tube is carried by a tilting cradle comprising a clip 47 secured to a channel piece 48 which is pivoted, by opposing pins 49, 50, in a supplemental bra ket 51 carried by the bracket 21. As the cradle tilts on its pivots the tube is tipped into an open-or-closed-circuit position as just described.

\Vhile the connection between the makeand-break device and the temperature-responsive element may vary, in structures embodying the invention to the best advantage it consists of mechanical elements and includes a part connected directly to the temperature-responsive element. It may conveniently comprise a leverage system iiicluding a compensating or lost motion connection. Although capable of various constructions, as here shown as an example, pivotally pinned to the free end of the steel bar 23 is a lever 52 fulcrumed in a forked lug 53 on the bracket 2l. As appears in Fig. 1, the fulcrum is close to the bar so that the bar movement, which, of course, is but slight, is several times magnified at the other end of the lever. Above the lever 52 is a second forked lug 54 in which is fulcrumed a second lever 55, this fulcrum also being located near the actuated end of its lever so as to further magnify the movement. For convenience the lever 52 may be designated as the lower lever and the lever 55 as the upper lever. The upper and lower levers are connected as later described. To connect the upper lever with the cradle, as here shown as an example, the upper end of lever 55 has a slot 56 in which rides a roller 57 on a pin 58 carried by a lug 59 on the cradle 48, formed by a part bent downwardly from one side of the cradle.

As later described in more detail, when the oven heats up to a given temperature, the expansion movement of the temperatureresponsive element operates the leverage system to cause the upper lever to act on pin 58 to tilt the cradle and thus break the circuit. Conversely, as the oven cools again, a reverse movement retilts the cradle back to horizontal position and recloses the circuit.

WVhile the lost motion or compensating connection between the bar 23 and the switch may vary in location and construction, with the leverage system described it is convenie'ntly located between the lower and upper levers; and in constructions embodying the invention to the best advantage it comprises a reverse-acting, duplicate spring arrangement, such that the lower lever will operate the upper lever only when the springs are equalized. Although capable of various constructions, as here shown as an example, pivoted to the free end of lower lever 52 is an abutment head 60 carrying a rod 61 which passes freely through an eye 62 formed on the lower end of u per lever 55. On the free end of the rod 61 IS an abutment nut 63 held in position by a lock nut 64 and oppositely faced with respect to abutment 60. Surrounding rod 61, between the abutment-60 and the eye 62, is a coil spring 65. A second and duplicatecoil spring 66 surrounds the rod between abutment nut 63 and the other side of eye 62. k

When the two springs are equalized, as in Fig. 5, the connection between the levers functions as a positive connection, in the manner of a plain link. That is, a right hand movement of the upper end of the lower lever moves spring against the eye 62 of the upper lever. This is opposed only by spring 66 which is equalized with spring 65. Consequently, the force impressed on eye 62 swings the upper lever and tilts the cradle, as above described,

Reversely, a left hand movement of the upper end of lever 52 forces spring. 66 (through rod 61 and abutment 63) against the other side of eye 62. This movement being opposed only by the equalized spring 65, the force impressed on eye 62 causes the upper lever to swing in the opposite direction and reversely tilt the cradle.

IVhen, however, the springs are not equalized one lever can and does move without actuating the other lever. That. is, referring to Fig. 1, for example, should the upper end of the lever move to the right, it pushes spring 65 against eye 62 of the upper lever. But the consequent movement of the upper lever is opposed by the greater compression of spring 66. As a result the upper lever remains stationary and the movement of lower lever 52 is compensated for by the movement of rod 61 through the eye and the expansion of spring 66. This compensating or lostmotion continues until the rod 61 has moved far enough to perm' spring 66 to expand to a condition equalizing it with spring 65..

The reverse situation will be apparent from Fig. 6, in which the spring 65 hasthe greater compression. In this position, the upper end of lever 52 is moving toward the left, the abutment 62 pushing spring 66 against eye 62 of the upper lever. But the upper lever cannot be moved until abutment 60 recedes far enough to permit equalization of the springs. Thus, it is noted that whenthe springs are equalized the upper lever can be operated to tilt the cradle in either direction and when they are not equalized the movement of the lower lever is taken up by the compensating expansion of one spring or the other. Consequently, the cradle is tipped only after a given movement of the tenperature-responsive device.

As later described, there is provided means for setting the control for various critical temperatures. For the present, let it be assumed that the control is arranged to operate for an oven heat of one temperature only, e. g., 400. It is assumed further that the hand switch 42 is closed and the oven cold. The mercury tube is horizontal, thus closing the circuit, whereby current is supplied to the heating element 19. The bar 23 has its extreme right hand position and spring 66 is under greater compression than spring 65. This condition is shown in Fig. 1. As the oven heats up, the expansion movement of the temperature-responsive element acts on lever 52 to swing its upper end to the right (as viewed in Fig. 1) thus pushing rod 61 to the right. As above described this movement is taken up by the compensating expansion of spring 66, and upper lever 55 remains without movement. This continues until the two springs are equalized, which position is illustrated in Fig. 5. This, as above described, leaves the upper lever free to be moved and the next increment of movement of lever 52 causes the upper end of lever 55 to swing to the left (Fig. 5). This movement, through the engagement of slot 56 with pin 58 tilts the cradle to the right (Fig. 6) so that the circuit is broken, as above described. During this latter movement of lever 55 spring 65 is slightly compressed, as indicated in Fig. 6. The showing is greatly exaggerated as 'the movement of the parts beyond the neutral point is but slight, being only such spring compression as is caused by the necessary movement of the upper lever to tilt the cradle.

In the Fig. 6 position the oven is assumed to be hotter than the critical temperature, e. g., 400, and the circuit is broken. As the oven cools the temperature-responsive element makes a reverse or contracting movement and the upper end of lever 52 moves to the left carrying with it rod 61 and abutment 63. Lever 55 remains fixed until the movement of lever 52 reexpands spring '65 to equalized condition. Upon the next increment of movement of lever 52 and rod 61, the pressure of spring 66 against eye'62, being new opposed only by equalized spring 65, swings lever 55 reversely and tilts the cradle back to former position. This causes the mercury to flow back to its level to connect the terminals and close the circuit. As long as the current is kept on by the hand switch the mercury tube will tip back and forth as the oven temperature rises and falls slightly beyond the critical point thus keeping is e oven temperature substantially constant.

In the above description reference has been made to .the compressed springs opposing movement oi. the upper lever in the direction the lower lever tends to move it. but the lot) lit)

tendency of the upper lever to be moved in the best advantage, this cradle control may also limit the movement of the cradle when it does tilt. These ends may be accomplished conveniently by cooperating stop elements one of which moves with the tube and at least one of which has two parts in offset relation. Although capable of various constructions, in that here illustrated as an example, the stop element moving with the tube is provided by the flat top 67 of the double-over wall of cradlle 48 and lug 50 (Fig. 2). Cooperating with this stop surface is a stop element comprising two stop lugs 68 and 69 carried by the bracket 51 and extending inwardly to overhang the stop surface 67 (Fig. 2). As appears in Fig. 1, for example, these stop lugs are offset from each other, or, in other words, they lie in different planes, so that one or the other may be engaged by the stop surface 67, depending on the position of the cradle.

hen the parts are in the position of Figs.

1 and 5, stop surface 67 abuts stop lug 68 so that the cradle cannot tilt to the left.

Stop surface 67, however, is spaced from stop 69 so that the cradle can tilt to the right. Consequently, in the Fig. 1 position,

while the force of compressed spring 66 against eye 62 tends to swing the upper end of lever 55 to the right, thus tilting the cradle to the left, this movement is prevented by the engagement of the stop surface 67 with stop lug 68. When the cradle has been tilted to Fig. 6 position, the situation is reversed. Stop surface 67 now engages stop lug 69 so that the cradle cannot tip further to the right and'this engagement prevents movement of the upper end of lever 55 to the left under the force on eye 62 of compressed spring 65. In this position, however, stop surface 67 has fallen away from stop 68'so that the cradle can retilt to circuit-closing position.

Moreover, these stops are so arranged as to limit the amount of movement through which the tube can tilt in its circuit opening and closing movements. That is, when the tube tilts from the position of Figs. 1, 5 and 10 to the position of Figs. 6 and 11, the stops serve to limit that tilt so that the mercury will not flow out of chamber 32, as above referred to. When the tube is reversely tilted the stops serve to limit the tube and cradle movement to the substantially horizontal, circuit-closing position.

In the above description one critical temperature only was considered. The invention in its entirey, however, includes means whereby the control may be set at any time for any critical temperature within a given range. This may be accomplished, for example, by varying the initial position of the upper lever. Although capable of various constructions, as here shown as an example, the parts are shifted for various critical temperatures b altering the position of the su plemental bracket 51, thereby to shlft t e upper lever. This bracket, as shown as an example, comprises a three sided structure pivoted by a pin 73 to 2. lug 74 on the main bracket 21. A critical temperature of 400 is, for convenience, considered as a neutral point. For this temperature, with the tube 30 horizontal, the upper lever and the supplemental bracket 51 are substantially vertical (Fig. 1). To set the control for higher or lower critical temperatures, the bracket 51 and upper lever are shifted to one side or the other of the vertical.

Assuming that the control is set for the neutral point, i. e., 400, and that the oven is at substantially that temperature, the mercury tube will be horizontal (Fig. 5) or tipped (Fig. 6) depending on whether the oven temperature is a small increment under or over 400 and in either case the bracket 51 will be in neutral or vertical position. Assuming further that it is desired to change the critical temperature to a figure lower than 400, the supplemental bracket 51, by means to be described, is shifted on its pivot to one side of the vertical: to the right as viewed in Fig. 7. This movement of the bracket, through the connections described, displaces the upper end of lever 55 in the same direction. If the mercury tube was tipped it remains tipped and if it was horizontal the consequent movement of the cradle tips it to openc1rcuit position. This movement of the upper lever cannot, of course, be transmitted to the lower lever because the latter can move only upon movement of bar 23, and, consequently the movement of the upper lever is compensated for by the compression of spring 65. The circuit being open, the oven begins to cool and the temperature-responsive element contracts and moves to the right as viewed in Fig. 7. The consequent movement of the lower lever is taken up by the expansion of spring 65 until the springs are equalized whereupon the con tinued movement of the lower lever swings the up er end of lever 55 in the direction to tilt t e cradle back to horizontal position, thus closing the circuit, which takes place when the oven reaches the new critical temperature. \Vith the supplemental bracket canted, the cradle and tube may not take true horizontal position but it will be near enough to cause the mercury to connect the two terminals. It will now be apparent that the lower it is desired to set the critical temperature, the more the supplemental bracket is shifted so that the more the upper lever is moved, the more spring 65 is compressed and the more the bar 23 must contract before the circuit is closed.

Let it be assumed again that the control was set for 400 and it is desired to adjust to a higher critical temperature. In this case, the supplemental bracket is shifted in the opposite direction to some such position as shown in Fig. 8. This swings the upper end of lever 55 to the left, the tube taking or-remaining in circuit-closing position as the case may be. The adjusting movement of the upper lever is taken up by the compression spring 66. Thereafter the switch remains closed as the oven temperature rises. As the temperature-responsive element expands the consequent movement of the lower lever is compensated for by expansion of,

spring 66 until the springs are equalized when the next increment of movement operates the lever 55 to tilt the cradle and open the circuit. The more the supplemental bracket is shifted, the more the spring is compressed and them'ofe the rod 23 must expand before the circuit is broken.

It will be seen, therefore, that the control canbe set for different critical temperatures, within a given range, by shifting the parts a given amount to one side or the other of a neutral position.

Other re-setting conditions will be understood from the above description. In this connection it is noted that should the control be reset from a point lower than the neutral to a point higher than the neutral, or vice versa, the bracket 51 and the upper lever 55 are shifted from one side of the vertical to the other side, the movement of the lower end of the lever resulting in the expansion of one spring (if compressed) and the compression of the opposite spring.

With-the construction described the control may be set for any desired critical temperature (within the given range) at any time, regardless of the previous setting and without waiting for the oven temperature and previous setting to coincide. .The compensating connection between the temperature-responsive element and the switch not only makes possible the actuation of the upper lever only at theend of a given movement of bar 23, but it also permits different settings to be made at an time.

There is provided calibrated means for setting the cradle in its various adjusted positions accordin to the critical temperature desired. Alt ou h capable of various constructions, in that ere shown as an ex ample, on the supplemental bracket 51 is.a pin 7 6 embraced by a oke or forked arm 75.

his latter is fastene to one end of a rock shaft 77. Secured to the other end of rock shaft 77 is a rocker arm 78 carrying a pointer 79 provided with a knob or handle 80. Secured to the side of the oven is a box-shaped quadrant or dial 81, on the arcuate edge of which are series of calibrated temperature markings, indicated at Fig. 3. The rocker arm 78 and pointer are enclosed within the quadrant exce t that the end of the olnter is offset, the 0 set portion extending t rough a slot 82 in the quadrant (Figs. 3 and 4).

The pointer carries a yoke 83 in which is slidable a spring-pressed shouldered pin 8 1 having a shoulder or collar 86 therein and which engages suitable detents 85 on the dial to hold the pointer in adjusted position. As appears in Fig. 3, the marking for 400, which has been taken, as above stated, as a neutral point, is half way between the limits of the range of temperatures indicated. As the pointer is moved to positions corresponding to temperatures lower than 400, the bracket 51 is shifted as above described, in connection with Fi 7 to corresponding positions. And as the pointer is moved to temperatures higher than 400, the bracket 51 is shifted in the opposite direction, as above described in connection with Fig. 8,

to corresponding positions.

The construction described provides a thermostatic control that is reliable, durable and economical. There are no relays to become dirty or frozenand fail to function. The temperature-responsive device must move and with the mechanical connection the cradle must consequently tilt and the mercury tube switch operate. It is, therefore, practically impossible for the control to fail to function. Service troubles are largely avoided as relays are dispensed with and the make-and-break device is-of a type that will practically never wear out electrically. The construction is available for all commercial voltages, and is simple and ecomonical to produce.

What I claim is:

1. In a device of the character described, and in combination, a temperature-responsive element, a tilting make-and-break device, a lever operated by the tmperatureresponsive element, a lever for tilting the ma e-and-break device, and a compensating connection between said levers whereby the second lever is actuated only at the end of a given movement of the first lever.

2. In a device of the character described, and in combination, a temperature-responsive element, a tilting make-and-break de vice, a lever operated by the temperatureresponsive element, a lever for tilting the make-and-break device, and a connection between said levers such that the second named lever is operated to tilt the make-and-break device at the end of a given movement of the first named lever.

3. In a device of the character described, and in combination, a temperature-responsive element, a tilting cradle, a make-andbreak device carried by said cradle and operated by the tilt thereof, a lever connected with the temperature-responsive element, a lever for tiltingsaid cradle, a rod connected with -said first named lever, oppositely faced abutments carried b said rod, a spri located between one a utment and the second named lever, and a duplicate sprin located between the opposite side of sai second named lever and the other abutment, and stop means for preventing movement of the second lever under the excess force of either spring while the springs are unequalized, whereby the action of the first named lever operates the second named lever only when the springs are equalized.

4. In a device of the character described, and in combination, a temperature-responsive element, a tilting make-and-break device, a lever actuated by the temperatureresponsive element, a second lever having a connection with the make-and-break device for tilting the same, and means for holding the second lever motionless during a given movement of the first lever and thereafter permitting movement of the second lever in one direction upon continued movement of the first lever.

5. In a device of the characterdescribed, and in combination, a temperature-responsive element, a tilting make-and-break device, a lever actuated by the temperatureresponsive element, a second lever having a connection with the make-and-break device for tilting the same, a compensating connection between said levers comprising reverseacting, duplicate springs arranged to cause the second lever to be operated by the first lever after such movement of the latter that the springs are equalized, and means for preventing, during such movement of the rst lever, movement of the second lever in the opposite direction, under the resultant force of the unequal compression of the springs.

6. In a device of the character described, and in combination, a temperature-responsive element, a tilting make-and-break device, a lever actuated by the temperature-responsive element, a second lever for tilting the make-and-break device, a compensating connection between said levers, comprising reverseacting, duplicate springs arranged so that the second lever will be operated by the first lever only when the springs are e ualized, cooperating stop elements of w ich one moves with the make-and-break device and at least one of which has two portions arranged in oilset relation, whereby one or the other of said portions is engaged by the cooperating stop element, depending on the position of the make-and-break device, such enga ement serving to prevent movement of die make-and break device under the force of the springs when unequalized.

7, In a device of the character described, and in combination, a temperature-responsive element a tilting make-and-break device, a movable bracket in which the makeand-break device is pivotally mounted, a lever actuated by the temperature-responsive element, a second lever for tilting the makeand-break device, a lost motion connection between said levers, and means for shifting the position of said bracket, thereby to vary the initial position of the second lever so that the make-and-break devce may be operated upon different movements of the first lever.

8. In a device of the character described,

and in combination, a temperature-responsive element, a tilting make-and-break device, a movable bracket in which the makeand-break device is pivotally mounted, a lever actuated by the temperature-responsive element, a second lever for tilting the make-and-break device, a lost motion connection between said levers, an indicator dial, a pointer movable along said dial, and a connection between said pointer and said bracket for shifting the position of the bracket as the pointer is moved, thereby to vary the initial position of the second lever so that the make-and-break device may be operated upon difierent movements of the first lever. I

9. In a device of the character described, and in combination, a temperature-responsive element, a tiltin make-and-break device, a lever actuate by the temperatureresponsive element, a second lever for tilt-- ing the make-andbreak device, a lost motion connection between said levers, and means, including a dial and a movable pointer, for

varying the initial positon of the second lever so that the make-and-break devce may be operated upon different movements of the first lever.

10. In a device of the character described, and in combination, a temperature-responsive element, a tilting device arranged to operate a heat-supply control element, a lever connected with the temperature-responsive element, a second lever for operating said tilting device, a rod connected with the first lever, oppositely disposed abutments carried by said rod, a spring located between one abutment and the second lever, and a duplicate spring located between the opposite side of said second lever and the other abutment, and stop means for preventing movement of the second lever under the excess force of either spring while the springs are unequalized, whereby the action of the first lever o crates the second lever only when the springs are equalized.

11. In combination, a lever for actuation by a movable element, a second lever for actuating a movable element, a rod connected with the first lever, oppositely disposed abutments carried b the rod, a springv lo-\ cated between one a utment and the second- .lever, and a duplicate s ring located bethe springs are unequali'zed, whereby the second lever is operated by the movement of the first lever only when the springs are equalized.

closing position, and a connection between,

the temperature-responsive element and said carrier consisting of mechanical elements and having a part secured to said temperature-responsive element.

18. In a device of theclass" described, and

in combination, a temperature-responsive.

element, a mercury tube switch comprising a tube having two depending chambers in which are located electric terminals, a tilting cradle in which said tube is mounted, a connection between said temperature-responsive element and said cradle for tilting the latter, and stop means for so limiting the tilt of the cradle that the tube is maintained 'in such position that said chambers always contain mercury enveloping their respective terminals.

14. In a device of the character described, and in combination, a temperature-responsivev element, a tilting make-and-break device, a lever connected with the temperatureresponsive element, a secondlever for tilting the make-and-break device, two duplicate springs for acting on the second lever in opposite directions, abutments movlng with the first lever and acting on the other ends of the springs and in opposite directions, whereby the second lever is actuated by the first lever when the springs are equalized, and stop means for preventing actuation of the second lever in the opposite direction while the springs are unequalized.

15. In a device of the character described,

and in combination, a temperature-responsive element, a tilting mercury tube switch, a lever actuated by the temperature-responsive element, asecond lever for tilting the mercury tube switch, a compensating connection between said levers, whereby the second lever is actuated only after a given movement of the first lever, and means for varying the initial position of the second lever so that the mercury tube switch may be operated upon various movements of the first lever.

16. In a device of the character described, and in combination, a temperature-responsive element, a tilting mercury tube switch, a

lever actuated by the temperature-responsive element, a second lever for tilting the mercury tube switch,..a' compensating connection between said levers, w ereby the second lever is actuated only after a given movement of the first lever, the second lever being movable on its fulcrum so as to be adjustable as toits initial position, whereby the mercury tube switch may be operated upon various movements of the second lever.

17. In a device of the character described, and in combination, a temperature-responsive element, a tilting make-and-break device, a lever actuated by the temperatureresponsive element, a second lever having a connection with the make-and-break device for tilting the same, a compensating connection between said levers comprising reverseacting, duplicate springs arranged to cause the second lever to be operated b the first lever after such movement of the latter that the springs are equalized, means for preventing, during such movement of the first lever, movement of the second lever in the opposite direction, under the resultant force of the unequal compression of the springs, and means whereby the initial position of the second lever may be varied, thereby to permit the make-and-break device to operate upon difierent movements of the first lever.

18. In a device of the character described, and in combination, a temperature-responsive element, a tilting cradle, a make-andbreak device carried b the cradle and operated by the tilt thereo a movable bracket in which said cradle is pivotally mounted, a lever actuated by the teinperature-responswe element, a second lever for tilting said cradle,- a compensating connection between said levers comprising reverse-acting, du licate springs arran ed to cause the secon lever to be operate by the first lever after such movement of the latter that the springs are equalized, means for preventing, during such movement of the first lever, movement of the,

second lever in the opposite direction, under the resultant force of the unequal com ression of the springs, and means for shilting the position of the second lever, to permit the make-and-break device to operate upon different movements of the first lever.

19: In a device of the character described, and in combination, a temperature-responsive element, a tilting make-and-break device, a lever fulcrumed adjacent one end and having its short arm connected with the temerature-responsive element, asecond lever ulcrumed adjacent one end and having its long arm connected with the make-and-break device, and an operating connection between the long arm of the first lever and the short arm of the second lever.

20. In a device of the character described, and in combination, a temperature-responsive element, a tilting make-and-break device, a. lever fulcrumed adjacent one end and having its short arm connected-with the tem perature-responsive element, a second lever fulcrumed adjacent one end and having its I actin long arm connected with the make-and-break device, a compensating connection between the long arm of the first lever and the short arm of the second lever comprising reverseduplicate springs arranged to cause the second lever to be operated by the first lever after such movement of the latter that the springs are equalized, and means for preventing, during such movement of the first lever, movement of the second lever in the opposite direction, under the resultant force of the unequal compression of the springs.

21. In a device of the character described, and in combination, a temperature-responsive element, a tilting make-and-break device, a lever actuated by the temperatureresponsive element, a second lever for tilting the make-and-break device, oppositely. faced abutments'on the respective levers, and a spring between said abut-ments for actuating the second lever from the first lever.

22. In a device of the character described, and in combination, a temperature-responsive element, a tilting make-and-break device, a lever actuated by the temperatureresponsive element, a second lever for tilting the make-and-break device, oppositely faced abutments on the respective levers, a spring between said abutments for actuating the second lever from the first lever, and means for preventing such actuation until the first lever has made a given movement.

In testimony whereof, I have hereunto set my hand.

SHERROD E. SKINNER. 

